What distinguishes a truck tractor from other vehicles?

A truck tractor is specifically designed to draw other vehicles, particularly semi-trailers, and does not typically carry a cargo load on its own. This unique configuration is what distinguishes it from other types of vehicles. Unlike a standard truck that may have a fixed bed and can carry freight by itself, a truck tractor serves the primary function of providing the power needed to pull trailers. Its design and purpose focus on towing rather than carrying freight within its own structure.

The other options describe characteristics that do not apply to a truck tractor: it is not a vehicle meant solely for personal transportation, nor is it built to operate independently in terms of freight carrying without the assistance of trailers. Thus, option C accurately captures the distinction of a truck tractor in the context of vehicle classifications.